Bromine/iodine containing compounds are key materials for producing peroxide curable elastomers. They are used as chain transfer agents (CTA) and/or as cure site monomers (CSM) in polymer synthesis. For example, diiodoperfluorobutane [I(CF2)4I] is a popular chain transfer agent.
Typically, α,ω-diiodo (per)fluoroalkanes are prepared by radical reaction of iodine with a fluoroolefin, reaction of ICF2I with a (fluoro)olefin, telomerization of a (fluoro)olefin with shorter-chained α,ω-diiodo fluoroalkanes, and coupling reactions of diiodofluoroalkanes.
Partially fluorinated α,ω-diiodo fluoroalkanes, such as I—CF2—CFH—CF2—I have been prepared by reaction of pentafluorocyclopropane (c-C3F5H) with iodine, as described in J. Am. Chem. Soc. 1995, 117, 5397-5398; or by the reaction of CF2I2 with trifluoroethylene (CF2═CHF), as described in J. Org. Chem. 2004, 69, 2394-2403.